High nitrates after switching to nilocg low tech

I have a 29 gallon fully planted tank that I've never had high nitrates in. I started dosing liquid nilocg 2 months ago. I recently started up a 40 gallon cichlid tank with some substrate I bought clean, but used. Upon testing my water a week after tank was set up, (and seeded with two active filters from 2 other tanks) I tested water with API master test. All was great but nitrates were 40 ppm. I blamed used substrate, and immediately changed 50% water and added prime. I retested and it was around 5-10 ppm, so today I redid the water change. But it was time to do 29 gallon so I went ahead and tested it too. The only thing changed is liquid ferts changed from Seachem Flourish to Niloc G low tech. My 29 gallon which has always read 0 nitrates, now has 20ppm. Are the nitrates registering because of niloc, and are they just as dangerous as if it were fish waste? The 29 is fully planted, 40 gallon is about 1/3 done being planted. I only dose every 2 weeks, and it's the recommended 1 pump per 5 gallons, but I dose 29 as a 20 gallon, and 40 has only been done once and as if it were a 35 gallon. Any suggestions? I tried to find this subject in forum but only found long winded fertilizer commentaries. I just need to know if my tanks are "falsely" showing dangerous nitrates, when it's just due to ferts. Fish were normal except in 40 gallon when it was 40 ppm, they were hiding, now all are great. Plants are great, they were stunted and had holes in leaves on seachem flourish..thank you!

 

The nitrates are coming from the Nilog. I would up your WC’s to 75% weekly. If you had 400ppm of nitrates then did a 50% WC your reading should have been 20ppm not 5-10.. you can get your plants going good again then just cut down on your dosage to one time a week or half doses weekly to see if that will keep them lower.

 

20-40ppm nitrates is just fine. Some would argue up to 80ppm is fine. Fertilizers essentially are nitrates. NilocG Thrive dosing is based on the Estimated Index (E.I.) method of dosing ferilizer. Which is a way of always having more nutrients in your tank than your plants actually need so there's never a chance of any plant deficiencies. Which is why they recommend a 50% or more weekly water change to "reset" your fert/nitrate levels each week.

 

Why a 50% or more? That would shock some of the more delicate fish. Why not just every weekend do two 50% pwc?

 

Why a 50% or more? That would shock some of the more delicate fish. Why not just every weekend do two 50% pwc?

The main reason to do %50 water changes when fertilizing with the E.I. method is you have to cut your nitrates back every week so nitrates don't continue climbing. Basically the same reason for any water change but with the E.I. method you need to do at least %50 to keep Nitrates balanced out.

Regardless large water changes of %50 or more weekly are pretty common practice and won't harm anything.

 

I do weekly 50-75% WC's weekly. I dose with Nilog Thrive and by the 5-7th day my Nitrates are usually above 20 Which i've grown accustomed to so that is the reason for my big weekly changes. And all my tankss are heavily planted. But they still get to that level using Thrive once a week.